America's Old Pipes Increase Gas-Leak Risk

Miles upon miles of underground cast-iron pipes are aging past 100 years, leading to dangerous leaks.

As durable as they may be, the thousands of miles of cast-iron pipes buried beneath our nation's oldest cities can't last forever. While residents of the Harlem neighborhood of New York City and Ewing, N.J., deal with the aftermath of recent fatal explosions tied to natural gas leaks, these and other cities around the nation must confront aging infrastructure.

Robert Jackson, a professor of environment and energy at Duke and Stanford universities, tells PopMech that pipe age is the No. 1 indicator in determining risk for leaking natural gas pipes. The older the city, the worse shape the pipes are in. For that reason, the biggest gas-leak problems come from cities on the East Coast. But "it is a broader issue than just the Northeast," Jackson says, adding that the problem can pop up in any older neighborhood.

For studies of Boston and Washington, D.C., Jackson found that the cast-iron pipes used until about 1950, many of which are now 100 years old or even older, led to thousands of leaks in each city, including nearly 6000 leaks in our nation's capital. Some of those leaks pushed methane concentrations to about 10 times greater than the threshold where explosions can occur. The team drove all 1500 road miles within Washington using a high-precision Picarro G2301 Cavity Ring-Down Spectrometer installed on a GPS-equipped car to map the leaks, leading to fixes along the way. While most leaks prove small enough to not cause major concern and others can easily dissipate into the air, that isn't always the case.

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Old pipes are susceptible to corrosion and cracking, and, in that case, gas needs somewhere to go. "Winter is a difficult time," says Mark McDonald, president of NatGas Consulting and New England Gas Workers Association. "When gas leaks outside the wall can't go into the air (because of frozen ground) they travel to the foundation and to every opening—water lines and sewer lines. If a foundation is porous or cracked, that is how it gets in."

A buildup of gas in a trapped environment heightens the risk for explosion as methane levels continue to increase. Able to combust on its own in the right environment, a simple spark or ignition within a pressurized gas environment is all that is needed for an explosion.

"Unfortunately, explosions are way too common and occur on a regular basis," McDonald says. "It appears to be getting worse."

Data from the U.S. Pipeline and Hazardous Materials Safety Administration shows an average of 70 injuries and 18 fatalities per year for the last 20 years. In all, the agency says, 359 people have died as the result of a gas-related explosion since 1994, and that doesn't include 2014 data.

In 1950 gas companies around the country began to install unprotected steel pipes instead of cast-iron, but that material isn't faring much better than the iron, Jackson says. It wasn't until about 30 years ago that plastic took over.

The United States has 1.2 million miles of gas pipe, with an average of 12 leaks per 100 miles. Just getting at these thousands of miles of pipe (New York City alone has more than 6300 miles of gas pipe) can prove not only time-consuming but also costly. Con Edison, one of New York's largest gas-pipe owners, replaces about 65 miles of pipe per year at a cost of $110 million, according to company data. It's already so expensive, Jackson says, that actually digging out a busted pipe and replacing it with plastic is rarely the course of action companies and cities choose; they typically opt for the more economical choice of sleeving the old pipes with new plastic when they can.

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In Massachusetts, McDonald says, he sees up to 800 broken pipes a year. A special "winter patrol" survey team looks for new cracks, but often can't keep up with finding all the new problem areas. And while New York's effort to upgrade pipe could replace the problem areas in as little as four decades, Jackson says it will take Philadelphia 80 years and Baltimore 140 years at their current rates.

These old pipes won't last forever, especially not another 140 years.

Tim Newcomb covers sports and infrastructure for Popular Mechanics. Follow him on Twitter at @tdnewcomb.

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